Dithiothreitol treatment rescues C1q assay performance by reducing high background

The presence of donor-specific antibodies (DSAs) to human leukocyte antigen (HLA) is associated with antibody-mediated rejection and reduced graft survival. Donor-specific HLA antibodies can bind to cells of the allograft and cause graft injury by activating the classical complement pathway. Antibodies capable of binding C1q, the first component of the classical complement pathway, are believed to be more detrimental to the graft. The C1q antibody assay is used to stratify the risk of antibody-mediated rejection. However, many patient samples exhibit extremely high background, rendering the test invalid. Here, we show that pre-treatment of sera with dithiothreitol (DTT) can eliminate high background in such samples, enabling detection of C1q-binding antibodies. Furthermore, the specificity of C1q-binding antibodies after DTT treatment is comparable to that observed without DTT treatment in samples that do not exhibit high background.